Treatment of cellulosic textile materials



latented May 27, 1941 UNlTED STATES "F @F TREATMENT OF CEILULOSICTEXTILE MATERIALS Thomas Henry Morton, Braintree, England, ml-

signor to Courtaulds Limited, London, England,

a British company No Drawing. Application April is, 1940, Serial No.330,425. In Great Britain April 4, 1939 3 Claims. (01. 260-:212)

This invention relates to the treatment of cellulosic textile materialswith formaldehyde.

It is well known to treat cellulosic materials with formaldehyde withthe object of obtaining yarious effects. For example, Eschalier in British Specification No. 25,647/06 has disclosed a process forstrengthening cellulose threads, films and the like which consists inimpregnating the formaldehyde and the acid catalyst before drying it, orsubjecting it to any other dehydrating conditions.

In carrying out the processof this invention the proportion of thesolution of formaldehyde to the cellulosemust be at least such that thecellulose is always in a fully swollen state. Generally it is preferredto have present however a considerably greater quantity of water than isnecessary merely .to produce this swollen state.

The time and temperature of the treatment with the solution offormaldehyde and acid catalyst will vary with one another, thetimerequired increasing rapidly as the temperature diminishes. The rateof absorption of formaldehyde by the cellulose will also depend uponthe-concentration of the acid and of the formaldehyde in the treatingsolution.

Using a solution containing 40 per cent of formaldehyde and sulphuricacid sufllcient to give a normal solution the reaction is substantiallycomplete in 10 minutes at 80 centlgrade;

washing and drying, the washing must be thorough and is preferablycarried outfirst in cold and then in but running water, while the dryingis preferably efiected at a temperature round about 100 centigrade.

' The cellulosic material may be in the form of cotton linters,bleached'wood pulp, or yarn or fabric prepared from natural orartificial fibres. The product obtained is difierent in many of itsproperties from that obtained by heating cellulose with formaldehyde andthen dehydrating. For example, whereas it has 'been stated that whenusing Eschaliers process about 0.2 to 0.3 per cent of formaldehyde iscombined with the,

cellulose, the product obtainedlaccording to the present invention maycontain up to 3 to 4 per cent, or even more, of combined formaldehyde,although we do not limit our invention to the productionofcompoundscontaining this pro- Portion of formaldehyde. If, for example, thetreating solution contains a smaller proportion of formaldehyde, theequilibrium is reached when smaller'proportions of formaldehyde arecombined with the cellulose. For instance, if the treating solutioncontains about 20 per cent of formaldehyde, the reaction equilibriumwill be reached when the cellulose contains about 1 per cent oimethylene oxide. The great differences between the products obtainedaccording to the present invention, and that described by Eschalierinthe aforesaid British Specification No. 25,647/06, and which isgenerally term sthenosaged cellulose, are that the products obtainedaccording to the-present invention show no increase in wet strength andpossess a high water imbibition, no increasedresistance to creasing anda slightly increased afllnity towards some direct dyes, all ofv whicheffects are contrary to those possessed by sthenosaged celluloseproduct's.

The product obtained according to the present invention reacts withnitrogenous compounds such as cyanamide and salts of tertiary bases, forexample pyridine and triethanolamine, to give materials having a goodafllnity for those dyes normally used for dyeing wool. Its use in thisconnection isdescribed in the co-flled joint application of JohnBoult'on andmyself, Serial No. 330,424. I

By heating the formaldehyde-cellulose product oi the invention in thepresence of an acid catalyst under dehydrating conditions, the pre- Ivlously known sthenosaged product with different properties can beobtained.

The following example illustrates one method I A of carrying out thepresent invention although the invention is not restricted to thisexample;

staple fibre marketed under the registered trade-marl: Fibro is immersedin 30 times its .volume of a 40 per -cent solution of formalde,

hyde acidified with sufficient sulphuric acid to form a normal solution,at 80 centigrade for minutes; The fabric is then removed from thesolution and washed, first in cold and then in hot running water untilall traces of uncombined formaldehyde and sulphuric acid are removed. Itis then dried at 105 centigrade for 30 minutes.

What I claim is: l. The production of compounds of! cellulose withformaldehyde by treating cellulose with an aqueous solution offormaldehyde containing a small proportion of an acid catalyst undersuch conditions of time and temperature that the reaction is allowed toapproach its equilibrium,- 'the proportion of the solution offormaldehyde to the cellulose being such that the cellulose is always ina fully swollen state, said solution 'containing 40% formaldehyde, saidcatalyst being sulphuric acid in decinormal to normal solution, saidtime being from 10 minutes to 24 hours, and said temperature being from24 C. to 80 C.

2. The production of compounds of. cellulose rium, the proportion of thesolution of formaldehyde to the cellulose being such that the celluloseis always in a fully swollen state, said solution containing 40%formaldehyde, said catalyst being sulphuric acid in decinormal to normalsolution, said time being from l0 minutes to 24 hours, and saidtemperature being from 24 C. to 80 0., removing the uncombinedformaldehyde and the acid catalyst from said compound, and thereaftersubjecting said compound to dehydra tion.

3. The production of compounds of cellulose with formaldehyde bytreating cellulose with an aqueous solution of formaldehyde containing asmall proportion of an acid catalyst under such conditions of timeand-temperature that the reaction is allowed to. approach itsequilibrium, the proportion of the solution of formaldehyde to thecellulose being such that there is present a considerably greaterquantity of water than is necessary merely to produce a fully swollencellulose, and the cellulose is thereby with formaldehyde by treatingcellulose with an aqueous solution of formaldehyde containing a smallproportion of an acid catalyst under such conditions of time andtemperature that thereaction is allowed to approach its equilibalways ina fully swollen state, removing the uncombined formaldehyde and the acidcatalyst from said compound, and thereafter subjecting the compound todehydration, said solution. containing 40% formaldehyde, said catalystbeing sulphuric acid in decinormal to normal solution, said time beingfrom 10 minutes to 24 hours, and said temperature being from 24 C. to C.

T. H. MORTON.

